Compositions for dissolution of low-k dielectric films, and methods of use

ABSTRACT

An improved composition and method for cleaning the surface of a semiconductor wafer are provided. The composition can be used to selectively remove a low-k dielectric material such as silicon dioxide, a photoresist layer overlying a low-k dielectric layer, or both layers from the surface of a wafer. The composition is formulated according to the invention to provide a desired removal rate of the low-k dielectric and/or photoresist from the surface of the wafer. By varying the fluorine ion component, and the amounts of the fluorine ion component and acid, component, and controlling the pH, a composition can be formulated in order to achieve a desired low-k dielectric removal rate that ranges from slow and controlled at about 50 to about 1000 angstroms per minute, to a relatively rapid removal of low-k dielectric material at greater than about 1000 angstroms per minute. The composition can also be formulated to selectively remove a photoresist layer, leaving the underlying low-k dielectric layer essentially intact.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/652,991, filed Aug. 31, 2000.

FIELD OF THE INVENTION

The present invention relates to compositions and methods for their usein cleaning or etching of wafers used in tire fabrication ofsemiconductor devices. More particularly, the invention relates tocompositions for selectively removing low-k dielectric layers and/orphotoresist layers on the wafers while controlling the rate of removalof the material, and methods using the compositions.

BACKGROUND OF THE INVENTION

Many semiconductor processes require wafer measurements to be made fromtime to time for production-line quality control, product stability, andconformance to specifications. Generally, the processing results areevaluated after each significant step. Since many tests are destructiveor will harm the product wafer, the measurements are typically performedon a test or “dummy” wafer, which are blank wafers that are mixed inwith the product wafers. Dummy wafers are specially prepared to havesimilar characteristics as the product wafers. Typically, a dummy waferis made of silicon, although other alternative materials have beendescribed. Since silicon wafers are expensive, when the processing andtesting is completed, the dummy wafers are usually cleaned, inspected,and reused. In the recovery or recycling of dummy wafers, it isimportant to provide a clean surface for subsequent processing. In therecycling of dummy wafers used in a masking photoresist process, it isimportant to completely remove blanket films of oxide and resist layersfrom the surface of the wafer down to the bare silicon.

Wet chemical processing is conventionally used for cleaning the surfacesof wafers. The cleaning is performed in order to produce a wafer havinga silicon surface that is hydrophobic and repels water as the wafer ispulled out of the bath. The wafers are then rinsed in deionized water,dried in heated nitrogen gas (N₂), and transferred to a processingoperation, or stored.

Aqueous mixtures of hydrogen peroxide (H₂O₂) and sulfuric acid (H₂SO₄)are commonly used to strip or remove photoresist from a wafer surfaceafter an etch processing step, or to remove a misaligned resist patternfrom a wafer for re-imaging after development and inspection (“rework”).In such applications, it is desirable that the layer that is presentunder the resist, including, for example, silicon dioxide, remainsintact on the wafer surface. In such cases, it is important to quicklyremove the photoresist layer without attacking the underlying material.However, organic components in an underlying low-k dielectric layer, canalter the selectivity of the dielectric material to a resist layer.

In other applications, it is desirable to completely remove the oxidelayer from a silicon surface. Hydrofluoric acid (HF) is conventionallyused as a component of oxide etchants. HF solutions provide selectiveetch rates of about 100:1 or better for SiO₂:Si, and effectively etchaway the oxide but not the underlying silicon wafer material. PrevalentHF solutions include, for example, a 1:10 mixture of 49% hydrofluoricacid (HF) and water, and a dilute 1:6 aqueous mixture of HF and ammoniumfluoride (NH₄F). However, wet HF chemistries have difficulty removinglow-k dielectrics such as a TMS-based low-k dielectric film, largely dueto organic components in the oxide films. As a result, cleaning with anHF solution can leave the wafer with a gummy organic residue on thesurface.

Therefore, it would be desirable to provide an improved composition fordissolution of low-k dielectric films from silicon-comprising surfaces.It would also be desirable to provide a cleaning composition that willcompletely remove low-k dielectric and photoresist components from thesurface of a substrate such as a dummy wafer. It would also be desirableto provide a composition that can be modified to provide removal of alow-k dielectric material such as a TMS-based low-k dielectric film,from a wafer surface over a range of removal rates according to theapplication at hand.

SUMMARY OF THE INVENTION

The present invention provides a cleaning composition for use in wetcleaning or etching of a wafer surface, and a method of cleaning oretching wafer surfaces by applying the composition.

The cleaning composition is an aqueous solution that includes one ormore effective amounts (v/v) of one or more fluorine-comprisingcompounds and one or more compatible acids to achieve the desiredselectivity to resist and/or a low-k dielectric, and the desired rate ofremoval of the low-k material and/or the resist. A preferred compositionaccording to the invention is an aqueous solution consisting essentiallyof the one or more fluorine-comprising compounds and the one or moreacids.

The cleaning composition can be modified according to the invention toprovide removal of a low-k dielectric material from the surface of asemiconductor wafer or other substrate over a range of removal ratesaccording to the application at hand. In particular, thefluorine-comprising compound and the amount that is used, and also theamount of the acid component that is used, can be varied according tothe invention to provide rapid removal of a low-k dielectric materialand/or organic materials such as photoresist from the surface of thewafer at a rate of removal of greater than about 1000 angstroms perminute, or to provide controlled removal of either or both of thosematerials from the wafer surface at a slow to moderate rate of removalof about 50 to about 1000 angstroms per minute. The composition of theinvention is useful in removing low-k dielectrics including, forexample, trimethylsilane- and dimethylsilane-based low-k dielectrics.

For example, the composition can be formulated for use in a processingstep such as a post-etch cleaning where it is desirable to remove low-kdielectric material at a slow and controlled rate so as to providebetter process control. In that case, the cleaning composition isformulated with a relatively dilute concentration of thefluorine-comprising compound. By comparison, in a dummy recyclingoperation after a photoresist deposition or etching step, it is highlydesirable to quickly and completely remove the low-k dielectric materialand any photoresist or other organic components that may be present fromthe surface of the wafer, whereby the surface of the wafer ishydrophobic and water sheets off the surface of a wafer. In that case, arelatively high concentration of fluorine-comprising component is usedin the composition. The composition can also be formulated to removephotoresist from a wafer, for example, after a mask operation, and leavethe underlying low-k dielectric layer intact.

Suitable fluorine-comprising compounds are those that will speciate orionize to provide fluoride ions at about pH 3 to 9. Thefluorine-comprising compound can be an inorganic fluoride compound suchas hydrofluoric acid (HF) and ammonium fluoride (NH₄F), or an organicfluoride compound such as tetramethylammonium fluoride and hydrogenfluoride pyridinium. Combined with the inorganic fluorine-comprisingcompound is an organic acid component that can be one or more of amonobasic, dibasic or tribasic organic acid, and is preferably citricacid, acetic acid, ascorbic acid, or mixtures thereof. An organicfluorine-comprising compound, when used, is combined with an inorganicacid such as sulfuric acid, among others. The acid component is includedin an amount to control the pH of the composition at about 3 to about 9.

The invention also provides a method of cleaning a surface of a wafer.One embodiment of the method includes providing an aqueous cleaningcomposition that includes at least one fluorine-comprising compound andat least one acid component, and has a pH of about 3 to about 9;providing a wafer having a low-k dielectric layer and an overlyingphotoresist layer on at least one surface; and contacting the surface ofthe wafer having the low-k dielectric material and photoresist layersthereon with the cleaning solution under conditions effective to removeboth of the low-k dielectric material and the photoresist layerssubstantially completely from the surface of the wafer, at a desiredrate of removal whereby the resulting cleaned surface of the wafer ishydrophobic and water sheets off the surface of the wafer.

Another embodiment of the method includes providing an aqueous cleaningcomposition that includes at least one fluorine-comprising compound andat least one acid component and has a pH of about 3 to about 9;providing a wafer having a masked or unmasked low-k dielectric materialon at least one surface; and contacting the surface of the wafer havingthe low-k dielectric material thereon with the cleaning solution underconditions effective to remove at least a portion of the low-k materialat a desired rate of removal.

A further embodiment of the method includes providing an aqueouscleaning composition that includes at least one fluorine-comprisingcompound and at least one acid, and has a pH of about 3 to about 9;providing a wafer having a low-k dielectric layer and an overlyingphotoresist layer on at least one surface; and contacting the surface ofthe wafer having the low-k dielectric and photoresist layers thereonunder conditions effective to remove the photoresist layer at a desiredrate of removal while leaving the a low-k dielectric layer essentiallyintact.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings which are forillustrative purposes only. Throughout the following views, referencenumerals will be used on the drawings, and the same reference numeralswill be used throughout the several views and in the description toindicate same or like parts.

FIGS. 1A-1B are general illustrations of cross-section of a wafer havinga layer of a low-k dielectric material and an overlying photoresistlayer on a surface, before and after cleaning, respectively, to removeboth layers from the surface of the wafer in accordance with oneembodiment of the method of the present invention.

FIGS. 2A-2B are general illustrations of cross-section of a wafer havinga layer of an unmasked low-k dielectric material on a surface, beforeand after cleaning, respectively, to remove the low-k dielectric layerin accordance with another embodiment of the method of the presentinvention.

FIGS. 3A-3B are general illustrations of cross-section of a wafer havinga layer of low-k dielectric material and an overlying photoresist layeron a surface, before and after cleaning, respectively, to remove thephotoresist layer from the wafer in accordance with another embodimentof the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides improved cleaning of a wafer surface in theproduction of semiconductor wafers. Aqueous blends of at least onefluorinated compound and at least one compatible acid are provided thatcan be optimized by task for removal of low-k dielectric material andphotoresist or other organic components from the surface of a wafer.

In accordance with the present invention, the compositions can beformulated to provide rapid removal of a low-k dielectric material, acontrolled low to moderate rate of removal of a low-k dielectricmaterial, removal of both resist and low-k dielectric materials, and/orremoval of photoresist material with selectivity to low-k dielectricmaterial. The blends are used for removal of a low-k dielectric layerand/or a layer of photoresist or other organic layer with selectivity toan underlying layer of a silicon substrate.

The fluorine-comprising compound which attacks the low-k dielectricmaterial, is combined with an acid component that assists in thedissolution of the organic components. The pH of the cleaningcomposition is maintained at an appropriate level by the addition of aneffective amount of the acid component to provide an environment forspeciation of the fluorine-comprising compound to fluorine ions, and toachieve the desired etch selectivity. At a pH >9, free fluorine isavailable only as fluoride ions (F⁻) which has little etching effect onsilicon oxide material. At a pH <3, the available fluorine species aredominantly molecular, i.e., HF and H₂F₂. At an about pH 3.5, there is amixture of species present. Preferably, the pH of the composition ismaintained at a pH of about 3 to about 9 such that the ionic fluorinespecies dominates. By adjusting the pH, the dominant species of fluorine(HF₂ ⁻ in the cleaning composition can be varied to adjust the etch rateon the low-k dielectric material.

Suitable fluorine-comprising compounds are those that speciate andrelease fluoride ions at a pH between about 3 to about 9. Examples ofsuitable fluorine-comprising compounds, i.e., include inorganicfluorines such as hydrofluoric acid (HF), ammonium fluoride (NH₄F), andmixtures thereof; and organic fluorines such as tetramethylammoniumfluoride, hydrogen fluoride pyridinium, triethylamine trihydrofluoride,and other straight, branched, cyclic or aromatic derivatives, andmixtures thereof.

In the use of HF, NH₄F, or other inorganic fluorine-comprising compound,the acid component is an organic acid. Suitable organic acids include,but are not limited to monobasic acids such as formic, acetic,propionic, n-butyric, isobutyric, and benzoic acid; dibasic acids suchas ascorbic, gluconic, malic, malonic, oxalic, succinic, and tartaricacids; tribasic acids such as citric and gallic acids; and mixturesthereof. In the use of an organic fluorine-comprising compound, asuitable inorganic acid is used, as for example, sulfuric acid,hydrochloric acid, nitric acid and phosphoric acid. The composition istypically in the form of a solution, and includes a solvent, preferablywater, for dilution of the components.

The cleaning composition includes the fluorine-comprising compound andacid component in an amount effective to provide the desired selectivityand etch rate for removal of low-k dielectric material and/or apolymeric photoresist. Combinations of various inorganic/organicfluorine-comprising compounds and organic/inorganic acids according tothe invention can be used for the desired results.

A first embodiment of a cleaning composition according to the inventionand a method for its use in cleaning or etching the surface of asemiconductor wafer, is described with reference to FIGS. 1A-1B.

Referring to the figures, a portion of a wafer 10 is shown prior tocleaning (FIG. 1A) and after cleaning (FIG. 1B). The wafer 10 includes asubstrate 12, for example, a silicon substrate, with a surface 14. Alayer or film of a low-k dielectric material 16 overlies the surface 14of the substrate 12. Overlying the low-k dielectric layer 12 areportions of an organic component 18 such as photoresist mask.

According to the invention a cleaning composition can be formulated toprovide complete removal of the photoresist layer 18 and low-kdielectric layer 16 from the surface 14 of the silicon substrate 12.FIG. 1B depicts the portion of the wafer 10 after cleaning, with thelow-k dielectric layer 16 and the photoresist layer 18 having beencompletely removed by the cleaning process, resulting in a hydrophobic,oxide-free silicon surface 14.

The substantially complete removal of both a low-k dielectric materialand a photoresist layer is particularly useful in the recycling of waferdummies where it is desired to completely remove all low-k dielectricand organic materials including a photoresist layer from the wafer downto bare silicon to produce a clean surface that is hydrophobic (i.e.,water sheets off the surface), for reuse of the wafer dummy inproduction.

A useful cleaning composition according to the invention for thesubstantially complete removal of a low-k dielectric material and aphotoresist layer or other organic material from the surface of asilicon-comprising semiconductor wafer is an aqueous solution thatincludes an inorganic fluorine-comprising compound such as HF, NH₄F, andmixtures thereof, and an organic acid such as citric acid, among others.

An example of a preferred composition to remove substantially all of alow-k dielectric material and a layer of photoresist or other organicmaterial from the surface of a wafer at a relatively low to moderatecontrolled rate of removal of about 50-1000 angstroms per minute toproduce a hydrophobic wafer surface, comprises an aqueous solution of anabout 1:2 (v/v) ratio of hydrofluoric acid (HF) and 50% citric acidand/or other organic acid, or about 30 to about 40% by volume of 49% HFand about 60 to about 70% by volume 50% citric acid and/or other organicacid, based on the total volume of the composition, with a pH of about 3to about 4, to provide a relatively moderate rate of removal of thedielectric and photoresist layers at about 400 to about 600 angstromsper minute.

Another useful composition comprises an aqueous solution of an about 2:1ratio (v/v) of 40% ammonium fluoride (NH₄F) and 50% citric acid and/orother organic acid, or about 60 to about 70% by volume of 40% NH₄F andabout 30 to about 40% by volume of 50% citric acid and/or other organicacid, based on the total volume of the composition, with a pH of about 4to about 6, to provide a relatively low rate of removal of the low-kdielectric layer at about 50 to about 150 angstroms per minute,preferably about 100 angstroms per minute.

To provide rapid removal of low-k dielectric material at a rate greaterthan about 1000 angstroms per minute, preferably greater than about 2000angstroms per minute, and minimal removal of a photoresist layer, apreferred composition is an aqueous solution of 49% hydrofluoric acid(HF) and 50% citric acid and/or other organic acid in a ratio (v/v) ofabout 2:1, or about 63 to about 70 percent by volume of 49% HF and about30 to about 36 percent by volume of 50% citric acid and/or other organicacid, with a pH of about 2 to about 5, to generally achieve a removalrate of about 2300-2700 angstroms per minute. Another useful compositionfor a relatively low rate of removal of a low-k material comprises anaqueous solution of 40% ammonium fluoride (NH₄F) and 50% citric acidand/or other organic acid in a ratio (v/v) of about 2:1, or about 63 toabout 70 percent by volume of 40% NH₄F and about 30 to about 36 percentby volume of 50% citric acid and/or other organic acid, with a pH ofabout 3 to about 6.

A cleaning composition for substantially complete removal of both alow-k layer and photoresist layer can also be prepared with an organicfluoride such as hydrogen fluoride pyridinium combined with an inorganicacid such as sulfuric acid. A preferred composition comprises an about1:5 ratio (v/v) of hydrogen fluoride pyridinium and 90% sulfuric acid(H₂SO₄), and/or other inorganic acid, or about 13 to about 19% by volumehydrogen fluoride pyridinium and about 80 to about 86% by volume of 90%H₂SO₄ and/or other inorganic acid, to provide a rapid rate of removal ofthe photoresist layer and a rate of removal of the dielectric layer atabout 700 angstroms per minute.

A second embodiment of a cleaning composition according to theinvention, and a method for its use is described with reference to FIGS.2A-2B. The wafer 30 to be cleaned includes a substrate 12, for example,a silicon substrate, and a surface 14. Overlying the surface 14 of thesubstrate 12 is an unmasked low-k dielectric film or layer 16 having athickness T₁.

According to the method, the cleaning composition is applied to thewafer 30 for removal of at least a portion of the low-k dielectric layer16 from the surface 14 of the silicon-comprising substrate 12. FIG. 2Bdepicts the portion of the wafer 30 after cleaning. As depicted, thethickness T₁, of the low-k dielectric layer 16 has been reduced tothickness T₂ by the removal process. The low-k dielectric layer 16 canalso be completely removed to produce a hydrophobic, oxide-free siliconsurface 14 as depicted in FIG. 1B.

The foregoing cleaning compositions can be formulated according to theinvention to provide removal of at least a portion of the low-kdielectric layer 16 from the surface of a semiconductor wafer at a rapidrate of removal (>1000 angstroms per minute) or a more controlled low tomoderate rate of removal (about 50 to about 1000 angstroms per minute).A slow and controlled removal of low-k dielectric films is desirable incases where removing the low-k dielectric material too quickly from thewafer leads to inadequate process control and causes difficulty inprocess integration. This is important when the objective is to removesmall amounts of the low-k dielectric, such as from a silicon contactarea. For example, in a post-etch cleaning, it is desirable toselectively remove a low-k dielectric material from a wafer at a slowand controlled rate in order to remove a small amount of the dielectricmaterial from an etched feature and leave the bulk of the film intact.In that case, a preferred etchant composition is one that is formulatedwith a dilute HF ratio.

The compositions can be used to selectively remove all or a portion of amasked low-k dielectric layer while leaving the photoresist maskessentially intact. Such a composition is useful where wet patterning isrequired (rather than RIE). The composition is formulated to provide anetch selectively ratio of about 50:1 to about 1000:1 (low-kdielectric:photoresist) whereby the low-k dielectric material isselectively removed without attacking the photoresist or other organicmaterial.

Another embodiment of a cleaning composition according to the invention,and a method for its use to remove photoresist from a wafer surfacewhile leaving an underlying low-k dielectric layer essentially intact onthe wafer surface, is described with reference to FIGS. 3A-3B. A portionof a wafer 40 is shown which includes a substrate 12, for example, asilicon substrate, with a surface 14. A layer or film of a low-kdielectric material 16 overlies the surface 14 of the substrate 12.Overlying the low-k dielectric layer 16 are portions of a photoresistmask 18. According to the method, a cleaning composition is applied to awafer 40 to provide selective removal of substantially all of thephotoresist mask layer 18, while leaving the underlying layer of low-kdielectric layer 16 essentially intact. FIG. 2B depicts the portion ofthe wafer 40 after cleaning, with the photoresist layer 18 having beencompletely removed by the cleaning process with the low-k dielectricmaterial remaining on the wafer substrate 12.

This cleaning method is particularly useful for removing a photoresistlayer after an etch processing step, or in a rework application toremove a misaligned resist mask. The composition is formulated toprovide an etch selectivity ratio of about 200:1 (photoresist:low-kdielectric) in which the photoresist material is selectively removed atabout 200 angstroms/minute without substantially attacking the low-kdielectric material, or a rate of removal of up to about 1angstrom/minute.

A useful composition for the sole removal of a photoresist mask layer orother organic layer overlying a low-k dielectric layer comprises anaqueous solution of an inorganic fluorine-comprising compound and amajor amount of an organic acid such as a 50% citric acid, with a pH ofabout 3 to about 4. A preferred composition comprises an about 1:100(v/v) of an inorganic fluorine-comprising compound and an about 20 toabout 60%, preferably about 40% to about 50%, aqueous solution of anorganic acid. Preferably, the inorganic fluorine-comprising compound isincluded in an amount of up to about 2% by volume, preferably about 0.5%to about 1.5% by volume, and the organic acid is included in an amountof up to about 99.5% by volume, preferably about 98.5% to about 99.5% byvolume, based on the total volume of the composition, with a pH of about3 to about 3.5. A preferred composition comprises an about 1:100 ratioof 49% HF and 50% citric acid and/or other organic acid, which providesa rate of removal of the photoresist layer at about 400-600 angstromsper minute with an etch selectivity (polymeric photoresistmaterial:low-k material) of at least about 200:1.

To clean a wafer surface according to the invention, the wafer is placedin contact with an appropriately formulated cleaning composition toremove the desired layer or layers at a desired rate of removal. Thecleaning composition can be applied using a conventional wet chemicalapplication technique as known and used in the art. For example, one ormore wafers can be placed vertically in a carrier or boat and thensubmerged in a recirculating bath of the cleaning composition, with orwithout agitation for about 5-10 minutes, depending on the thickness ofthe layer to be removed. The cleaning composition can also be sprayedonto the surface of the wafer. Preferably, a substantially constantconcentration of the reactive components of the cleaning composition isbrought into contact with the wafer surface so that a uniform rate ofremoval can be maintained to allow for process uniformity and thedesired extent and completeness of removal.

In the cleaning of a wafer, the cleaning composition can be used at atemperature of about 15° C. to about 30° C., preferably at about 15° C.to about 30° C. High temperatures of about 40 to about 60° C. can betypically used to achieve faster etch rates. In a selective removal of aphotoresist mask or other organic material and not a low-k dielectriclayer, it is preferred that lower temperatures of about 15° C. to about30° C. are used to improve the selectivity of the low-k dielectricmaterial over the photoresist.

Depending on the composition of the cleaning composition, otherselective etch ratios/rates are within the scope of the presentinvention. The selectivity and removal time can be adjusted andcontrolled by varying the concentrations of the fluorine-comprisingcompound and the acid component, as further illustrated in the examples.The selectivities vary as the v/v ranges increase and decrease.Generally, a composition formulated to comprise a major amount of HFwill provide a high etch of the low-k dielectric material selective tothe resist. With a major amount of the acid component and a lowercontent of the fluorine-comprising compound, good removal of the resistselective to the low-k dielectric material will be achieved.

The following examples are given to illustrate specific preferredembodiments of the present invention. Numerous other variations,however, are within the scope of the present invention.

EXAMPLE

This example studies the effect of varying the fluorine-comprisingcomponent (49%HF of 40% NH₄F), and the v/v ratios of thefluorine-comprising component and the acid component (50% citric acid)on the rate of removal of a low-k dielectric and a photoresist layer(OIR 897-10I) from a silicon wafer surface.

TABLE 1 Low-k Fluorine Acid removal rate Photoresist Run # componentParts (v) Component Parts (v) (Å/min.) Removal 1 49% HF 100 — —^(a)negligible ^(a)negligible 2 49% HF 100 — — ^(b)negligible^(b)negligible 3 40% NH₄F 2 50% citric acid 1  100 negligible 4 49% HF 250% citric acid 1 2500 negligible 5 49% HF 1 50% citric acid 2  500complete 6 49% HF 1 50% citric acid 100 Negligible complete 7^(c)Hydrogen 1 90% sulfuric acid 5 Complete (700) Complete fluorinepyridinium (anhydride) ^(a)Repeated acid/water dips over 30 minutes,produced non-uniform flaking without dissolution of the low-k dielectricor photoresist. ^(b)A single, prolonged immersion (20 + minutes) showedlittle or no effect on removal of the low-k or 10i photoresist. ^(c)Thewafer surface had a 3000 angstrom layer of trimethylsilane (TMS) only(no photoresist layer).

The surface of the wafers had a layer of chemical vapor deposited (CVD)trimethylsilane-based low-k dielectric film (TMS delivered in H₂ andN₂O) about 3000 angstroms thick, and an overlying layer of photoresist.The wafers were immersed in a beaker of the cleaning solution. Run Nos.3-6 were immersed in solution for multiple tests, from 30 seconds to 4minutes. The low-k dielectric removal rates were determined by using aUV1250 spectroscopic ellipsometer.

The results show that changing the fluorine-comprising component, andvarying the amounts of the fluorine and acid components alters the rateof removal of a layer of low-k from the wafer surface.

The results of Run Nos. 1-2 show that HF used alone was ineffective inremoving dielectric and photoresist material from the wafer surface. Theuse of HF alone resulted in pieces of the TMS-based low-k dielectricfilm and photoresist flaking off and floating on the surface of thecleaning solution, without significant dissolution.

The results of Runs 3 and 4 show the effect of varying the inorganicfluorine component that is used on the rate of removal of the TMS-basedlow-k dielectric layer. A 2:1 of NH₄F:citric acid provided a low-kdielectric removal rate of about 100 angstroms per minute, while a 2:1of HF: citric acid provided a low-k dielectric removal rate of about2500 angstroms per minute.

The results of Run Nos. 4-6 show the effect of varying the weight ratioof the organic acid (50% citric acid) and the fluorine component (HF) onthe rate of removal of the TMS-based low-k dielectric film and apolymeric photoresist mask layer from the surface of the wafer. A 1:100HF:citric acid ratio resulted in complete removal of the photoresistwhile leaving the low-k layer intact on the surface of the wafer. A 1:2HF:citric acid ratio resulted in complete removal of both thephotoresist and the TMS-based low-k dielectric film layers, with amoderate rate of removal of the low-k layer at about 500 angstroms perminute. A 2:1 ratio of HF:citric acid ratio resulted in rapid removal ofTMS-based low-k dielectric film at about 2500 angstroms per minute, andnegligible removal of photoresist.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents. The disclosure of cited patents are incorporated byreference herein.

1. A composition for cleaning or treating a surface of a semiconductorwafer, comprising: an aqueous solution of hydrogen fluoride pyridiniumand an inorganic acid in a ratio of about 1:5 (v/v) to remove organicmaterial and low-k dielectric material from the surface of the wafersuch that the surface of the substrate is rendered substantiallyhydrophobic; wherein the composition has a pH of about 3 to about
 9. 2.The composition of claim 1, wherein the inorganic acid is selected fromthe group consisting of sulfuric acid, nitric acid, hydrochloric acid,phosphoric acid, and mixtures thereof.
 3. A semiconductor wafer cleaningcomposition, comprising: an aqueous solution comprising hydrogenfluoride pyridinium and an inorganic acid in a ratio of about 1:5 (v/v),wherein when applied to a surface of the wafer, the compositioneffectively removes organic material and low-k dielectric materialtherefrom to render the surface hydrophobic.
 4. The composition of claim3, wherein the inorganic acid is selected from the group consisting ofsulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, andmixtures thereof.
 5. The composition of claim 3, wherein the dielectricmaterial is removed at a rate of about 50 to about 1000 angstroms perminute.
 6. A semiconductor wafer cleaning composition, comprising: anaqueous solution comprising an organic fluorine compound and aninorganic acid in a ratio of about 1:5 (v/v); the organicfluorine-comprising compound selected from the group consisting ofhydrogen fluoride pyridinium, triethylamine trihydrofluoride, andmixtures thereof; wherein when applied to a surface of the wafer, thecomposition effectively removes organic material and low-k dielectricmaterial therefrom to render the surface hydrophobic.
 7. The compositionof claim 6, wherein the dielectric material is removed at a rate ofabout 700 angstroms per minute.
 8. A semiconductor wafer cleaningcomposition, comprising: an aqueous solution comprising an organicfluorine compound and an inorganic acid in a ratio of about 1:5 (v/v);the organic fluorine-comprising compound selected from the groupconsisting of hydrogen fluoride pyridinium, triethylaminetrihydrofluoride, and mixtures thereof; and the inorganic acid selectedfrom the group consisting of sulfuric acid, nitric acid, hydrochloricacid, phosphoric acid, and mixtures thereof; wherein when applied to asurface of the wafer, the composition effectively removes organicmaterial and low-k dielectric material therefrom to render the surfacehydrophobic.
 9. A semiconductor wafer cleaning composition, comprising:an aqueous solution comprising hydrogen fluoride pyridinium and aninorganic acid in a ratio of about 1:5 (v/v); wherein when applied to asurface of the wafer, the composition effectively removes organicmaterial and low-k dielectric material therefrom to render the surfacehydrophobic.
 10. A semiconductor wafer cleaning composition, comprising:an aqueous solution comprising hydrogen fluoride pyridinium and aninorganic acid in a ratio of about 13:86 to about 19:80% by volume;wherein when applied to a surface of the wafer, the compositioneffectively removes organic material and low-k dielectric materialtherefrom to render the surface hydrophobic.
 11. The composition ofclaim 10, wherein the dielectric material is removed at a rate of about50 to about 1000 angstroms per minute.
 12. The composition of claim 10,wherein the dielectric material is removed at a rate of about 700angstroms per minute.
 13. A semiconductor wafer cleaning composition,comprising: an aqueous solution comprising hydrogen fluoride pyridiniumand an inorganic acid in a ratio of about 13:86 to about 19:80% byvolume; wherein when applied to a surface of the wafer, the compositioneffectively removes organic material and low-k dielectric materialtherefrom to render the surface hydrophobic, the dielectric materialbeing removed at a rate of about 50 to about 1000 angstroms per minute.14. The composition of claim 13, wherein the dielectric material isremoved at a rate of about 700 angstroms per minute.
 15. A cleaningcomposition, comprising: an aqueous solution of an organic fluoride andan inorganic acid in an about 1:5 (v/v) ratio effective to removeorganic material and dielectric material to render a surfacehydrophobic; the organic fluoride selected from the group consisting ofhydrogen fluoride pyridinium, triethylamine trihydrofluoride, andmixtures thereof.